Photographic antihalation layers



March 25, 1969 G. MGGUCKIN 3,434,839

PHOTOGRAPHIC ANTIHALATION LAYERS Filed June 1. 1965 3\ coLoR EMULS/O/VLAYER em/ fF/LTER LAYER 4 \fCOLO/P EMULSION LAYER 5 coLaR EMULSION LAYERfA/vm/ALAr/o/v LAYER zm SUPPORT A rr oRzvEYs United States Patent3,434,839 PHOTOGRAPHIC ANTIHALATION LAYERS Hugh G. McGuckin, Rochester,N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey Filed June 1, 1965, Ser. No. 460,244 Int. Cl. G03c 1/84,7/20 US. C]. 96-84 27 Claims ABSTRACT OF THE DISCLOSURE Toned Carey Leasilver and antihalation layers comprsing toned Carey Lea silver areprovided by reacting Carey Lea silver with sufiicient thiol compound totone the Carey Lea silver gray. The antihalation Carey Lea silver can beused in photographic elements particularly in multilayer photographiccolor films and can be conveniently removed in customary processing ofthe element.

This invention relates to photographic elements and more particularlyrelates to antihalation components of photographic elements.

It is desirable to have in photographic products some form ofantihalation layer which absorbs light in order to avoid undesirablereflections from the film base or from interfaces between the emulsionlayer or layers and the film base which if not avoided cause additionaldiffused exposure of the silver halide emulsion.

Among the more recent methods used for preventing halation is the use ofdye-containing pelloids, the socalled gray silver underlayer, and carbonblack dispersed in a polymeric or colloidal binder. The use of graysilver suffers from requiring substantial amounts of silver to providean acceptable density for use as an antihalation layer, and the use ofcarbon black dispersed in a binder is particularly disadvantageousbecause of the resulting contamination of the solutions used inprocessing the exposed photographic element;

Furthermore, when dye layers are used, the neutral density which isdesired has usually required two or three dyes to obtain a neutralabsorption of the light. This is particularly important in colorprocesses requiring a neutral density layer such as that disclosed inMillikans patent application Ser. No. 159,057, filed Dec. 13, 1961, andnow abandoned.

In some of the antihalation methods used heretofore, an antihalationlayer containing, for instance, pigments or dyes or carbon black iscoated on the reverse side of the film base or support. Normalprocessing of the exposed film in an alkaline developer solution causesthe antihalation layer to be dissolved away, thus contaminating thedeveloper solution.

Silver antihalation layers are used because the silver is subject tobleaching in ferricyanide type bleach solutions which are conventionallyused with silver halide emulsions intended for the formation of coloredimages. For instance, silver particles have been used in antihalationlayers in what has been known as gray silver. These gray silverparticles have a size of at least 0.1 micron. However, the gray silvercoating has been relatively expensive due to the necessity forsufficient silver to provide adequate density and also due to theparticle size of the silver used.

Carey Lea silver has been well known as a filter layer particularly foruse in multilayer photographic products where it has served to filterout certain wavelengths. However, it has not been possible tosatisfactorily tone Carey Lea silver to provide an antihalation layer,although it would be less expensive to use a silver having a much3,434,839 Patented Mar. 25, 1969 smaller particle size and which hasgreater covering power than the gray silver. Moreover, the presence ofCarey Lea silver in a layer contiguous to a silver halide emulsion hasin some instances been detrimental since the Carey Lea silver acted asnuclei for the physical development of silver during the firstprocessing step using a conventional black-and-white developer. In suchan element, the Carey Lea silver particles would act as sites on whichsilver from a silver halide emulsion would be deposited, therebyreducing the density of the resulting silver image formed in the silverhalide emulsion.

For these reasons, it was desirable to find some means not only oftoning the Carey Lea silver, but also providwhen used as an undercoatbut which could be processed in normal photographic processing to atransparent film without contaminating the processing solutions. Such anantihalation material must be compatible with the lightsensitiveelement, such as a silver halide emulsion, and should not appreciablyaffect the speed of the emulsion when utilized as a contiguous layer.

I have now discovered that an advantageous antihalation material isCarey Lea silver toned neutral, which at the same time obviates thedisadvantage of having Carey Lea silver as sites for physicaldevelopment. In addition, the tone Carey Lea silver has greater coveringpower than gray silver with the advantage of lower cost.

One object of this invention is to provide an improved antihalationlayer which can be rendered transparent in a conventional silverbleaching solution. Another object is to provide a method of toningCarey Lea silver so it can be used for an antihalation layer. A furtherobject is to provide less expensive silver-containing antihalationlayers. A still further object is to provide multilayer color elementscontaining an antihalation layer which can be rendered transparent in aconventional bleach solution. An additional object is to provide a CareyLea silver antihalation layer which does not provide sites for physicaldevelopment from a contiguous silver halide emulsion. Another object isto provide an antihalation material which is compatible with alight-sensitive emulsion and which does not have an appreciable effecton the speed of the silver halide emulsion when used as an antihalationundercoat. A further object is to provide an antihalation undercoathaving a greater density and being made from readily availablematerials.

The discovery is unexpected in view of the prior arts teaching that thetoningof a conventionally chemically developed silver image produces acolor which is other than neutral such as a sepia tone which is entirelyunsuitable for use in an antihalation layer. It is furthermoreunexpected that Carey Lea silver could be toned a neutral black whichwould have a greater density for use as an antihalation material thanthe gray silver used heretofore.

In one embodiment, my invention comprises an antihalation compositionfor use with photographic elements comprising Carey Lea silver tonedneutral with an amino alkylthiol oligomer or mixture thereof asillustrated by the following general formula:

N[( 0 H2) mS] r-Z R2 wherein R and R represent hydrogen atoms oridentical alkyl groups such as, for example, methyl, ethyl, or propyl,or identical hydroxyalkyl groups such as, for example, 2-hydroxyethyl,or 2-hydroxy-l-propyl, or, taken together,

represent a saturated ring of five or six atoms such as, for example,morpholinyl, or piperidyl, or, if R represents hydrogen, or methyl, Rrepresents hydrogen or hydroxyalkyl groups such as, for example,Z-hydroxyethyl, l,l-dimethyl-Z-hydroxyethyl,l,l-(dihydroxymethyl)-ethyl, tris- (hydroxymethyl)methyl, glucosyl, mrepresents a small integer between one and five, n represents an integerbetween one and four or a fraction between one and four, and Zrepresents a hydrogen atom or a moiety which is replaceable by a silveratom.

The oligomers useful in my invention are low molecular weight polymericmaterials containing one or more alkylene sulfide chains. Commonly,these materials are prepared as mixtures of several chain lengths and itis convenient to represent the structure by showing it as an averagevalue for the different chain lengths which may be present. In somecases, It will be a fraction such as, for example, 1.25.

Such oligomers include aminoalkanethiols, aminoalkylenethioalkanethoils,etc., and their derivatives in which the terminal hydrogen is replacedby oragnic groups such as hydroxymethyl, iminocarbamoyl and the like, orby a metal replaceable by silver, in aqueous solution, advantageouslyunder alkaline conditions, for example, zinc or zirconium. It will beseen from the foregoing that the oligomers useful in my invention may bein the thiol form or those in which the hydrogen of the thiol group inthe oligomer is replaced by a moiety from which the free thiol may bereadily formed in aqueous solution. For example, in the case ofisothiuronium salts which contain the iminocarbamoyl group in place ofhydrogen, treatment with alkali will split off the cyanamide group andthe thiol will be formed; specifically, from3-dimethylaminopropylisothiuronium chloride hydrochloride, the3-dimethylaminopropanethiol will be formed. In the case wherein thethiol derivative is a rnercaptal wherein the thiol hydrogen is replacedby a hydroxyemthyl group, the thio is readily generated. For example,2-dimethylaminoethy1 hydroxymethyl sulfide will yield2-dimethylaminoethanethiol. In the case of salts formed with the thiolcompound with metal ions, the particular metal replaceable by silver,for example, the cadmium salts of diethylaminoethanethiol may be usedeffectively. Metals of group III; for example, zinc, and metals of groupIVb such as zirconium are useful.

In a particularly useful embodiment, I use diethylaminoethanethiol totone Carey Lea silver. For use as an antihalation agent, it is normal todispose the toned Carey Lea silver in a binder of the kindconventionally used in preparing silver halide emulsions, such asproteinaceous colloids, including gelatin, casein or zein, and syntheticpolymeric substances such as polyvinyl alcohol, polyacrylates,hydrolyzed cellulose esters or cellulose ethers. In the event that theantihalation layer is to be used on the back of a film support, thebinder could be one of those removable in an alkaline solution, such ascellulose acetate phthalate, cellulose ether phthalate,polyvinylphthalate, or polyacrylate.

Carey Lea silver may be prepared according to Luppo- Cramer, Koll.Zeitschrift, vol. 8, p. 240, 1911.

In another embodiment, my invention comprises a photographic elementhaving a support (or base) which has coated thereon at least onelight-sensitive silver halide emulsion coating and at least oneantihalation layer containing Carey Lea silver toned neutral with anaminoalkanethiol having the above general formula. Such photographicelements may be adapted for either black-andwhite photography or colorphotography and may have a plurality of light-sensitive silver halideemulsion layers. They may also have one or more antihalation layers, forinstance, an antihalation layer on each side of the support. Any of theconventional supports may be used, such as cellulose acetate, paper,glass, metals such as aluminum as is used in lithography, a polyestersuch as polyethylene terephthalate, polystyrene, polyolefins such aspolyethylene, etc.

The support may be given a preparatory treatment in order to improveadhesion, such as electron bombardment, oxidation or flame treating, orother treatments known in the art.

In an additional embodiment, my invention involves the process ofneutral toning Carey Lea silver by mixing a liquid suspension of CareyLea silver with an aqueous solution of the aforesaid aminoalkanethiolcompounds. The toning of the Carey Lea silver occurs very rapidly uponmixing the solution and the thiol compound. It is desirable that theliquid solution also contain some gelatin or other binder in which thetoned Carey Lea silver is to be dispersed when applied as anantihalation layer. After the toning of the Carey Lea silver, additionalbinder may be added to the resulting mixture.

The ratio of thiol to Carey Lea silver may be varied widely, from abouta molar ratio of 30:1 to about 1:1. Within these limits no more than theeffective amount is desirable, not only from an economic standpoint butbecause the thiol compounds are, in general, silver halide complexingagents and an excess could affect the processing agents. The amount ofneutral toned Carey Lea silver, usually expressed as milligrams persquare foot of surface area of the support of the photographic element,to be used varies depending upon the character of the support, thecharacter of the binder in which the Carey Lea silver is dispersed andthe intended use of the photographic element. Illustratively, sufiicienttoned Carey Lea silver is used to provide a range of from about 5 toabout milligrams per square foot of support surface area.

It will also be understood that the antihalation materials hereindisclosed may be used with advantage in a diffusion transfer systemwhere the light-sensitive emulsion is coated on a paper support. Theymay also be used in colloid transfer systems and in the formation oflithographic plates where the emulsion is coated on a support whichprecludes the use of an antihalation layer which must be removed in itsentirety.

The light-sensitive emulsion which may be used with the toned Carey Leasilver antihalation material of this invention may be sensitizedchemically or spectrally employing compounds heretofore known for suchsensitization. Such material may also be used with light-sensitive acidpolymer layers as disclosed in US. Patent No. 2,948,610; light-sensitivecinnamic acid ester polymers disclosed in US. Patent No. 2,690,966;bichromate sensitized materials such as those disclosed in US. PatentNo. 2,448,861; the light-sensitive layers described in US. Patent No.3,903,800; and in the product described in US. Patent No. 2,607,683.

These antihalation layers are particularly valuable when used with coloremulsions, particularly those that have dye-forming couplers containedtherein which react with the oxidation products of a paraphenylenediamine type developing agent. They may also be used with the color typeemulsions in which the dye-forming coupler is supplied from theprocessing solution. In these processes, it is conventional to use ableach step such as an oxidizing bleach in removing the silver image.This bleach step bleaches the Carey Lea silver antihalation layerrendering it transparent, but permitting such layer to remain as part ofthe photographic element. It will be appreciated that such antihalationlayers can be used whether the color element is on an opaque supportsuch as paper or whether it is on a transparent support such as filmbase. It is also useful in conventional multilayer photographicelements, and in those color processes where the multilayer colorelement is used to produce the color print by diffusion to a mordantedreceiving sheet, although in this particular adaptation it would not benecessary to bleach the Carey Lea silver antihalation layer.

The annexed drawing illustrates diagrammatically a photographic elementcomprising a neutral toned Carey Lea silver antihalation layer made andused in accordance with this invention. The antihalation layer 1,comprising a neutral toned Carey Lea silver dispersed in gelatin, isdisposed on a cellulose acetate film support 2. On top of theantihalation layer 1, are a plurality of color layers 3, 4 and 5 whichcomprise light-sensitive silver halide gelatin emulsions containingdye-forming couplers, each layer of which is sensitized to a respectivelight range so that the resulting element will contain images in thecyan, magenta and yellow colors. A conventional filter layer 6 isinterposed between color layers 3 and 4 and comprises a dispersion ingelatin of untoned Carey Lea silver having its natural yellow color.

. It is to be understood that, although the photographic elementdepicted in the drawing is a multilayered product intended for colorphotography, a photographic element intended for black-and-whitephotography might comprise merely support 2, antihalation layer 1, and alight-sensitive silver halide emulsion layer disposed in the position oflayer 5, but not having the dye couplers used to make color layers.

The following examples are intended to illustrate my invention but notto limit it in any way.

EXAMPLE 1 The antihalation underlayer coated over a cellulose acetatesupport consisted of, on each square foot, 258 milligrams of gelatin and17.6 milligrams of Carey Lea silver. Preparation was as follows:

Milliliters Carey Lea silver (31.9 milligrams of silver per gram of 5%gelatin solution) 6.0 Diethylaminoethanethiol-HCI in water, 5% 39.0Sodium hydroxide, 0.25 N 3.0

The above components were held minutes at 45 C., with stirring.

Fifty milliliters of 5 percent gelatin were added and the mixture waschill-set, shredded, and washed under running water (40 F.) for 2 hours.

A hardener and coating aid were added before coating.

EXAMPLE 2 Portions of the antihalation underlayer of Example 1 wereeasily bleached and rehalogenated in approximately 1 second at roomtemperature in each of the following solutions:

(1) Potassium ferricyanide grams 100.0 Potassium bromide do 200 Water tomake 1.0 liter.

(2) Potassium dichromate grams 9.5

Concentrated sulfuric acid milliliters 12.0 Potassium bromide grams 10.0Water to make 1.0 liter.

(3) Potassium permanganate 1 grams 2.0 Concentrated sulfuric acid"milliliters" 10.0

Water to make 1.0 liter.

1 No rehalogenation results with this solution.

A portion of the bleached area in each case was easily fixed in 1 minuteat room temperature using Kodak Fixing Bath F-S.

The effect on the color of Carey Lea silver by the compounds shown belowwas determined by the following procedure: One milliliter of Carey Leasilver dispersion containing 25 milligrams of silver per gram of 5percent gelatin solution which had the characteristic yellow color wasspread on a glass surface. Several drops of a saturated solution of thecompounds listed below were added to the Carey Lea silver solution andmixed thoroughly. The moisture was evaporated off leaving the thincoating. The color of the layer was observed by transmitted andreflected light. The compounds listed below were effective in toning theyellow Carey Lea silver to a neutral.

Z-hydroxyethylaminooligoethylene sulfide-1 HOCH CH NH (CH CH S) H2-hydroxyethylaminooligoethylene sulfide-1.35

HOCH CH NH(CH CH S) H Z-hydroxyethylaminooligoethylene sulfide-1.67

HOCH CH NH (CH CH S) H 2-hydroxyethylaminooligoethylene sulfide-2 HO CHCH NH (CH CH S) H N-{i-irydroxyethyl)-N-methylaminooligoethylenesulfider HO CH OHzNKJHzCHZSlLnHN-(Z-aminoethyl)-N-hydroxyethylaminooligoethylene sulfide-1 .30

HO CHzCHz N(CH2C 2S)1.ao

HzNCHzOH N- (Z-aminoethyl) -N-hydroxyethylaminooligoethylenesulfide-2.42

H0 CHzCHz N(CH2CH2S)2.42H

HZNCHZC 2 Bis (2-hydr0xy-1-propyl) aminooligoethylene sulfide-3.47

OH (OHAIJHCHQZN (OH2CH2S)3 41H 3-dimethylaminopropylisothiuroniumchloride hydrochloride O NCHzOHzSH 2-allylaminoethanethiol CH =CHCH NHCHCH SH Di-sec-butylaminoethanethiol C H C H2 N-CHzCHzSH CH3 OHCHzZ-dimethylaminoethylmercapto zinc chloride hydrochloride2-hydroxy-1,1-dimethylethylaminooligoethylene sulfide-1.69

CH3 HO 0H2( JNH oH2oH2s)r.iir1

1, 1- (dihydroxymethyl) -propylaminooligoethylene sulfide-3 .43

CHzOH CH CH G-NHWHzCHzShJuH N-methylglucosylaminooligoethylenesulfide-3.1

OH; HO GH (CHOH) OHZI I(CHzCHzS)a.1H

7 EXAMPLE 3 A fast bromoiodide emulsion, optically sensitized to greenlight and containing a magenta forming pyrazolone coupler was coatedover the following:

(1) A plain gelatin layer.

(2) A regular CLS layer.

(3) A CLS layer toned neutral by the method described in the invention.Spectrophotometric measurements in this layer confirmed the neutralityof this layer.

All coatings were made on clear cellulose acetate support. Coatings weregiven sensitometric exposure and processed to a color reversal,employing a bleach step to remove the silver image.

Two sets of samples were exposed. A blue exposure was used for one setto measure the inherent emulsion sensitivity. The second set was given aminus blue exposure to measure the green sensitivity. The followingsensitometric data were obtained.

Minus blue exposure Blue exposure Feature Dmnx Relspeed Dmx Rel. speedThe lower speed for the latter two coatings is expected and indicativeof the light absorption by the undercoat.

The D data indicate that there is no significant reduction in densitywhen the neutral toned CLS is used.

Regular CLS is unsuitable as a color film underlayer because of itefiiciency in catalyzing physical development during the firstblack-and-white development step, thereby removing silver halide fromthe adjacent couplercontaining layer. Less silver halide remains for thesecond or color development step, resulting in a lower maximum density.Toning the CLS by the method of this invention, in addition to providinga neutral color, reduces its catalytic activity for physicaldevelopment, thereby permitting its incorporation in a color film.

Spectral sensitivity curves show the toned Carey Lea silver to have asgood a neutral tone throughout the visible spectrum as a carbon neutraldensity filter except for slightly more transmission in the red region.

It was possible to obtain an optical density of 0.7 from a silvercoverage of 17.6 mg. of silver/ sq. ft. leading to a covering power ofabout 40. The covering power of gray silver is less than 30. The tonedCarey Lea silver in one embodiment was therefore 1.3 times moreefiicient in light absorption than was the gray silver.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

I claim:

1. A toned Carey Lea silver comprising Carey Lea silver which has beenreacted with sufficient thiol compound to tone said silver gray, saidthiol compound comprising at least one compound having the generalformula:

N m n 2) S] Z R2 wherein R and R are selected from the class consistingof H, lower alkyl, lower hydroxyalkyl, lower polyhydroxyalkyl, andnonmetallic atoms necessary to complete the heterocyclic ring from 5 to6 atoms, In represents an integer of 15, n represents a number between 1and 4 and Z represents a moiety replaceably by silver.

2. A toned Carey Lea silver of claim 1 in which the said silver has beenreacted with said thiol compound in a molar ratio of 1:30 to 1:1.

3. A photographic element comprising a support having thereon at leastone layer comprising a toned Carey Lea silver of claim 1.

4. A photographic element comprising a support having thereon at leastone layer comprising a toned Carey Lea silver of claim 1 in which saidCarey Lea silver has been reacted in a molar ratio of 1:1 to 1:30 withsaid thiol compound.

5. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part diethylaminoethanethiol HCl per part of saidsilver.

6. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part 2-hydroxyethylaminooligoethylene sulfide perpart of said silver.

7. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part 2-hydroxy-l,1-dimethylethy1aminooligoethylenesulfide per part of said silver.

8. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part morpholinoethanethiol per part of saidsilver.

9. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part 1,1 (dihydroxymethyl) ethylaminooligoethylenesulfide per part of said silver.

10. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part tris (hydroxymethyl) methylaminooligoethylenesulfide per part of said silver.

11. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part bis(2 hydroxy 1 propyl)aminooligoethylenesulfide per part of said silver.

12. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part N-methyl glucosylaminooligoethylene sulfideper part of said silver.

13. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part N (2 aminoethyl) 2hydroxyethylaminooligoethylene sulfide per part of said silver.

14. A photographic element comprising a support having thereon at leastone antihalation layer comprising Carey Lea silver reacted in a molarratio of at least one part zinc salt of diethylaminoethanethiol HCl perpart of said silver.

15. A process of toning Carey Lea silver comprising reacting Carey Leasilver with suflicient thiol compound to tone said silver gray, saidthiol compound comprising at least one compound having the generalformula:

wherein R and R are selected from the class consisting of H, loweralkyl, lower hydroxyalkyl, lower polyhydroxyalkyl, and nonmetallic atomsnecessary to complete the heterocyclic ring of from 5 to 6 atoms, mrepresents an integer of l5, n represents a number between 1 and 4 and Zrepresents a moiety replaceable by silver.

16. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least ope part diethylaminoethanethiolHCl per part of said s1 ver.

17. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part 2hydroxyethylaminooligoethylene sulfide per part of said silver.

18. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part 2 hydroxy 1,1dimethylethylaminooligoethylene sulfide per part of said silver.

19. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part morpholinoethanethiolper part of said silver.

20. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar'ratio of at least one part 1,1 (dihydroxymethyl)ethylaminooligoethylene sulfide per part of said silver.

21. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part tris (hydroxymethyl)methylaminooligoethylene sulfide per part of said silver.

22. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part bis(2 hydroxy 1 propyl)aminooligoethylene sulfide per part of said silver.

23. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part Nmethylglncosylaminooligoethylene sulfide per part of said silver.

24. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part N (2 aminoethyl) 2hydroxy ethylaminooligoethylene sulfide per part of said silver.

25. A process for toning Carey Lea silver comprising reacting the CareyLea silver in a molar ratio of at least one part zinc salt ofdiethylaminoethanethiol HCl per part of said silver.

26. A photographic element comprising a support having thereon at leastone layer comprising a toned Carey Lea silver of claim 3 and at leastone light sensitive silver halide emulsion.

27. A photographic element comprising a support having thereon at leastone layer comprising a toned Carey Lea silver of claim 3 in which saidCarey Lea silver has been reacted in a molar ratio of 1:1 to 1:30 withsaid thiol compound, and at least one light sensitive silver halideemulsion.

References Cited UNITED STATES PATENTS 2,688,601 9/1954 Herz 96-843,232,759 2/1966 White et al. 96-52 XR NORMAN G. TORCHIN, PrimaryExaminer.

RONALD H. SMITH, Assistant Examiner.

US. Cl. X.R.

